Compare files excluding certain lines.

Quick tip, you can use any expression for the sed commands in the (). With this trick you can redirect the stdout of 2 commands to the diff command. This might become very useful, if you want to compare 2 files, excluding the first line.

diff <(sed '1d' file) <(sed '1d' file2)

More interesting example is where the string ABC is converted to abc before comparing in the second file with the following command: